1. Field of the Invention
The present invention relates to an image recording apparatus, a notch forming apparatus, and a method for use therewith, more particularly, relates to an image recording apparatus for forming a positioning reference on a sheet-shaped image recording material such that the image recording material is positioned and mounted on a predetermined mounting member, a notch forming apparatus for forming the positioning reference, and a method for forming the positioning reference.
2. Related Art Statement
Conventionally, color printed materials are produced through a number of processes such as an exposure process (which serves as an image recording process), a printing process, and the like. Prior to the exposure process, an original image of a color printed material is separated into a plurality of colors, which typically are: Y (Yellow), M (Magenta), C (Cyan), and K (Kuro, i.e., “black”). Thus, image data of the respective colors are generated. Such image data are supplied to a cylindrical outer surface scanning apparatus which is used for an exposure process. The cylindrical outer surface scanning apparatus incorporates a recording drum. On the outer surface of the recording drum, a sheet-shaped plate which serves as an image recording material, e.g., a so-called PS plate (Presensitized Plate) or a thermal plate, is mounted. A “PS plate” is a plate comprising a plate material (e.g., an aluminum plate, a plastic sheet, or paper) and a photo-sensitive layer preapplied on the plate material.
In the exposure process, the cylindrical outer surface scanning apparatus subjects the plate which is mounted on the outer surface of the recording drum to an exposure process in order to form an image of each of the respective separated colors on the plate based on the image data thus supplied. In other words, in the case where the original image is color-separated into Y, M, C, and K, the cylindrical outer surface scanning apparatus draws images of the four different colors on four plates.
A printing machine which is used in a printing process applies inks to the plates which have been exposed, each ink being in a color corresponding to the associated plate, so as to overlay the respective images on a final color printed material. If the images of one or more colors are misaligned with each other when overlaid, the resulting color printed material will be of an inferior quality. In order to prevent such misalignment between images, positioning holes for the printing process, which are used as a positioning reference during the printing process, are formed in predetermined positions in the plate, prior to the exposure process. Each plate can be positioned in place by fitting pins which are provided on a printing drum of the printing machine into the positioning holes for the printing process. In some cases, e.g., where the specific printing machine to be used is still undecided at the prepress stage, the positioning holes for the printing process may be formed after the prepress.
Misalignments between images may also occur if the positions of one or more images drawn during the exposure process are misaligned with respect to the plates of the corresponding colors. In order to prevent such image misalignments with respect to the plates during the exposure process, in U.S. Pat. No. 6,321,651 and Japanese Laid-Open Patent Publication No. 2002-341561, for example, positioning for a plate is performed on the outer surface of the recording drum of the cylindrical outer surface scanning apparatus.
A plurality of offset pins are provided in an apparatus disclosed in U.S. Pat. No. 6,321,651 for positioning each plate in place by changing an angle of the plate in accordance with the width thereof, such that only two pins contact an edge of the plate.
In the cylindrical outer surface scanning apparatus disclosed in Japanese Laid-Open Patent Publication No. 2002-341561, positioning pins for positioning each plate in place are provided on the outer surface of the recording drum. Together with the holes for the printing process, positioning notches for the recording drum are provided along one end of the plate, the positioning notches being configured so as to receive the positioning pins. Hereinafter, referring to FIG. 31, an outline of a plate positioning method employed in the cylindrical outer surface scanning apparatus disclosed in Japanese Laid-Open Patent Publication No. 2002-341561 will be described. FIG. 31 is a schematic view showing the simplified relative positions of the plate P, punches 501a to 501c of punchers 500a to 500c, and positioning pins 601a to 601c of a recording drum 600.
In FIG. 31, the cylindrical outer surface scanning apparatus disclosed in Japanese Laid-Open Patent Publication No. 2002-341561 includes three punchers 500a to 500c. The punches 501a to 501c are provided in the punchers 500a to 500c, respectively. The puncher 500a is provided to create a positioning notch which receives the positioning pin 601a. The punch 501a has a cross section in the shape of a full circle with the radius r. The punchers 500b and 500c are provided to create a non-contacting notch by which the plate P is not in contact with the positioning pins 601b and 601c. Each of the punches 501b and 501c has an elongated-circular cross section. The punches 501a to 501c are arranged in such a manner that the respective centers thereof are on the single line, with a pitch Q1 between the centers of the punches 501a and 501b, and a pitch Q2 between the centers of the punches 501a and 501c. 
When a plate P having the lateral width L is led into the puncher 500, the plate P is led into an inlet of the puncher 500, so that the positioning members disposed at the back ends of the inlet come in contact with a leading end face Pe of the plate P. Specifically, the plate P is positioned in such a manner that the end face Pe coincides with or extends in parallel to the line on which the centers of the punches 501a to 501c are aligned (the illustrated plate P1 is in this state). Depending on the width L of the plate P, the punchers 500a to 500c operate to form necessary notches along the end face Pe of the plate P by the punches 501a to 501c. For example, in the case where a plate P has the width L as shown in FIG. 31, the punch 501a of the puncher 500a and the punch 501b of the puncher 500b operate to form a positioning notch Pae and a non-contacting notch Pbe, respectively, along the end face Pe of the plate P.
On the other hand, three positioning pins 601a to 601c are provided on the outer surface of the recording drum 600. Each of the positioning pins 601a to 601c has a cross-section in the shape of a full circle with the radius r. The positioning pins 601b and 601c are located at an offset of a distance r along the circumferential direction of the recording drum 5 with respect to the positioning pin 601a. The positioning pins 601b and 601c are disposed at the intra-central pitches Q1 and Q2 from the positioning pin 601a, respectively, along the axial direction of the recording drum 600.
In the case where the plate P which is prefabricated with the positioning notch Pae and the non-contacting notch Pbe is positioned on the recording drum 600 with the positioning pins 601a to 601c provided thereon, the plate P is positioned in place as the positioning pin 601a fits in the positioning notch Pae of the plate P and the end face Pe of the plate P abuts with the positioning pin 601c. Note that the plate P is not in contact with the positioning pin 601b because of the non-contacting notch Pbe being formed (the illustrated plate P2 is in this state).
In accordance with the conventional cylindrical outer surface scanning apparatus, a plate is positioned in place in such a manner that two positioning pins are in contact with a positioning notch and an end face of the plate, respectively. A non-contacting notch is formed so that the plate is not in contact with the positioning pins which are not used for positioning. Specifically, only the positioning notch Pae is formed in a short-width plate P, and the short-width plate P is positioned in place by utilizing the positioning pins 601a and 601b. The positioning notch Pae and a non-contacting notch Pce, which is formed by a puncher 500c, are formed in a medium-width plate P, and the medium-width plate P is positioned in place by utilizing the positioning pins 601a and 601b (the positioning pin 601c is not in contact with the plate P due to the non-contacting notch Pce). As shown in FIG. 31, the positioning notch Pae and the non-contacting notch Pbe are formed in a long-width plate P, and the long-width plate P is positioned in place by utilizing the positioning pins 601a and 601c (the positioning pin 601b is not contact with the plate P due to the non-contacting notch Pbe).
As described above, in order to prevent image misalignments with respect to the plates during the exposure process, positioning pins for positioning each plate in place are provided on the outer surface of the recording drum of the cylindrical outer surface scanning apparatus. Together with the holes for the printing process, positioning notches for the recording drum are provided along one end of the plate, the positioning notches being configured so as to receive the positioning pins. Thus, the positioning notches for the recording drum and the positioning holes for the printing process are formed in each plate prior to an exposure process. During the exposure process, the positioning notches for the recording drum can be used as a reference for aligning the images to be exposed. During the printing process, the positioning holes for the printing process can be used as a reference for aligning the images to be printed.
However, in accordance with the apparatus disclosed in U.S. Pat. No. 6,321,651, some plates having a certain width maybe positioned in an unstable manner. Specifically, in the case where the plate is disposed so as to be in abutment with two positioning pins, a plate whose corner is barely in contact with a third pin located at the outer side of any of the two positioning pins cannot be stably positioned due to its width. Also, in the case where the accuracy of the end face of a plate is not insured, such inaccuracy may affect the positioning accuracy.
Also, in accordance with the cylindrical outer surface scanning apparatus disclosed in Japanese Laid-Open Patent Publication No. 2002-341561, a center of the two positioning pins being in contact with a positioned plate is misaligned with respect to a center of the plate. Such a misalignment may result in instability of positioning of the plate. In addition to this, the puncher 500a is always used for creating a positioning notch, whereas the punchers 500b and 500c are always used for creating a non-contacting notch. In other words, since the positioning notch Pae created by the puncher 500a is always used for positioning, a lateral width of the plate P extendable in the direction of the positioning notch Pae (i.e., the right side of FIG. 31) is restricted. Furthermore, a positioning pin to be always used is fixed, thereby reducing positioning flexibility of the plate to be stabilized on the recording drum.